


Last Mech Standing

by perictione (leclairage)



Series: Last Mech Standing [1]
Category: The Transformers (Cartoon Generation One), Transformers - All Media Types, Transformers Generation One
Genre: Creative Negotiation Techniques, Enemies to Lovers, Fragging for Peace, M/M, Oral Sex, Plot What Plot/Porn Without Plot, Sex competition, Size Kink, Sticky Sexual Interfacing
Language: English
Status: Completed
Published: 2019-01-12
Updated: 2019-01-12
Packaged: 2019-10-08 13:46:54
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,351
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17387471
Author URL: https://archiveofourown.org/users/leclairage/pseuds/perictione
Summary: It had all been decided in the middle of a battle. Before Optimus had known what was happening, somehow they’d agreed that control of the planet Earth would be decided by single ‘combat’ between himself and Megatron, where the loser was the one who couldn’t overload anymore.





	Last Mech Standing

**Author's Note:**

  * For [RHplus](https://archiveofourown.org/users/RHplus/gifts).



> This is a belated Christmas gift for the incredible RH, who bribed me with candy and this absolutely stunning premise. Enjoy!

Optimus had made a mistake. A very big mistake.

Actually, a wildly large mistake. A massive, gigantic, throbbing mistake. A mistake so big, it stretched the limits of belief, and would probably stretch some other things, and stretch them very, _very_ well.

He should probably stop looking at it.

Yes, this was crossing into staring now, and he really should look away. He should look at anything else really. But instead Optimus reset his optics, just to be sure that thick, long, gorgeous, unspeakable thing was—

Megatron snapped his fingers in front of Optimus’s face.

Optimus jumped, and looked away from Megatron’s enormous spike. It bobbed a little in the air.

It was easily one of the most erotic things Optimus had ever seen.

“I did warn you, Prime,” Megatron said, smirking.

Optimus winced.

How had everything already gone wrong? This was _not_ the way things were supposed to go _at all._

Optimus had had a plan. Or, not a plan, exactly. It wasn’t a strategy. Optimus had had _expectations._ He’d come here expecting to—very graciously—allow Megatron to spike him. It was going to be a gesture of goodwill, even. And, maybe, he’d thought that Megatron would particularly _like_ that idea, because getting to spike a Prime seemed like the sort of thing that might turn Megatron’s crankshaft. And, maybe, if Megatron particularly _liked_ whatever they were doing, then Optimus might have had an edge.

That is, in the competition.  

Alright, it might have been a strategy.

But even if Megatron had realized it was a strategy on Optimus’s part, he still wouldn’t really be able to refuse when Optimus very generously volunteered to be the receptive partner—

Right. Well. This had backfired spectacularly.

Optimus cleared the static out of his vocalizer. “I take your point.”

It would take gentle, steady, focused effort to prepare Optimus’s valve to take something of that size without injury. Optimus couldn’t really imagine _Megatron_ doing that—no, nevermind, he could imagine it. He could imagine it in great detail. Megatron leaning over him, his fingers stretching Optimus’s valve, that ridiculous smirk on his face, probably taunting him as Optimus writhed, and Optimus would be able to see that enormous spike eagerly pressurized and waiting between Megatron’s legs the whole time—

Optimus shut down the start-up sequence for his cooling fans, again.

It just wasn’t likely to happen. Megatron wasn’t especially known for his patience. But the bigger problem was, there was no way Optimus would last. He enjoyed all aspects of interface, but a large spike was...a special interest. Not that ‘large’ was an accurate description of the monstrosity in front of him now. ‘Large’ implied some amount of reasonableness in terms of scale. Megatron’s spike was...entirely unreasonable. Optimus knew it was physically possible for him to take it, however. Before they’d fled Cybertron, he’d possessed several interface aids of a similar size. He’d regretted losing them. But a real, living, charged spike was an entirely different thing. He’d always wanted, always dreamed—

“There’s still time to back out, you know.” Megatron was grinning, insufferably, probably thinking that Optimus was afraid of it, or something else ridiculous. Still, better that he think that than the truth.

Megatron’s spike was just the size Optimus had imagined in his filthy, self-indulgent fantasies of being stretched to the absolute limits of what his valve could take. If Megatron did spike him, Optimus would overload in seconds, and then, well, it wouldn’t take very long before Megatron would win their wager. Why had he thought agreeing to this was a good idea?

“I’m not backing out.” Optimus would never give in. Not to Megatron. “But in the interest of time, perhaps I should spike you instead.”

“Well, I’m sure you know your valve better than I do.”

“I know I wasn’t designed to take shuttles,” Optimus grumbled. Not that he _couldn’t._ Optimus had checked.

Megatron only chuckled, and went to sit on the unnecessarily large berth.

The unnecessarily large, unnecessarily luxurious berth.

Optimus had agreed to allow the Constructicons to build a temporary structure for this exercise, but he hadn’t expected it to be quite so blatantly...like this. Wheeljack had supervised to make sure there were no tricks, but the result had still been a huge berth, a stack of soft blankets, and what Optimus could only describe as ‘mood lighting.’ Was that a bottle of artificial lubricant on the nightstand? And who had thought they’d need a nightstand?

Optimus hadn’t exactly intended to martyr himself going through with this proposition, but he’d wanted to at least maintain the illusion that he was doing this for the Autobots. Definitely not for some other reason. This room reminded him more of what it must have been like to take a romantic vacation on Old Cybertron. It made it hard to remember that he was just taking one for the team.

Or, giving one for the team, as it turned out.

Megatron laid down until he was lounging indolently against what looked like a pile of very supportive pillows—did the Decepticons just have these sorts of things lying around? Then, Megatron—

Then, Megatron spread his thick, powerful legs and let his valve panel transform open as he lightly stroked his spike. There was a teasing glisten of lubricant in between dark valve lips, and the glow of his anterior node matched the smoldering coal red of his optics. Optics that were narrowed above a proud smile, like he was delighted to put himself on display for Optimus.

“Do you know what to do with a valve, Prime?”

Optimus sputtered static. “Yes, Megatron, I do, and—”

“Then why are you standing there like you’ve never seen one before?” Megatron stretched leisurely, completely unconcerned. His legs parted a little bit more. “Aren’t you supposed to be good at this?”

Optimus thought with both pride and embarrassment of how certain Autobots had shouted support for him when they’d made this ‘agreement’. Sideswipe had cheered, “Frag his lights out, Prime!”

It had all been decided in the middle of a battle. He’d been grappling Megatron, rather well at the time, and Starscream had made some jibe about it. Before Optimus had known what was happening, the argument had escalated, and somehow they’d agreed that control of the planet Earth would be decided by single ‘combat’ between himself and Megatron, where the loser was the one who couldn’t overload anymore. Or who yielded, whichever came first.

Prowl had tried to talk him out of it, but by then Optimus had given his word...

He’d let his anger get the best of him, really. But until this moment, Optimus had really thought he would win. He had a not-undeserved reputation among the Autobots for being a very satisfying lover. It was actually a point of pride. He was generous, and attentive, and he had plenty of stamina, which everyone he’d ever brought to his berth had appreciated very much.

Now, Optimus felt off balance. How had Megatron managed to stay one step ahead of him this whole time?

“Prime, for this to work, you are going to have to get your spike out.” Megatron was looking disdainfully at Optimus’s modesty panel. “You aren’t shy, are you?”

Optimus was torn between twin desires to release his spike and to power up his energon axe and put it through Megatron’s smug face. But that would be as good as admitting he was ‘shy.’ So Optimus opened his panel and allowed his spike to pressurize.

To his embarrassment, his spike was already releasing preparatory fluid in a little stream. Optimus probably should have expected that he’d be...affected by this whole scenario. He hadn’t considered that when he’d decided to commit to the idea. It made it all the more likely he would lose.

Megatron made a considering sound, and Optimus refocused on his face. “I suppose you’ll do,” Megatron said.

“Oh, will I?” Optimus said, indignant.

Megatron didn’t even respond, like Optimus wasn’t even a threat, he just waved a hand, gesturing his opponent forward.

Feeling like his spike had made the decision, Optimus went. He climbed onto the berth on his hands and knees, facing Megatron and Megatron’s exposed valve. And, who could forget, Megatron’s smug face. Optimus felt a droplet of fluid drip down from his spike onto the berth.

Megatron was obviously enjoying the view. His still-exposed spike twitched as he watched Optimus crawl towards him, and he smirked. Optimus had to admit, he was enjoying the view as well _—Megatron_ spread out and exposed and waiting—but it galled him that he was enjoying this so much. Practically ordering him around, making him crawl across the berth—although, Optimus thought, if that charged him up, all the better. Optimus was determined to overload Megatron until he couldn’t overload again for love or money or the war effort.

Speaking of, he might as well get a headstart on that. That valve certainly did look inviting…

Optimus moved forward and wrapped one arm around one of Megatron’s thighs and steadied himself with a hand on his opponent’s opposite hip. He snapped open his battle mask, then leaned over, until he was low on the berth and his face was hovering close to Megatron’s valve.

Megatron looked down at him, frowning now, though Optimus could hardly see him around his giant spike. Now that Megatron had pressurized his spike, manually returning it to an unaroused state behind his panel was...possible, but would be very uncomfortable. Optimus was going to have to stare at it for the rest of this encounter.

“Shall I prove to you that I know what I’m doing?” Optimus asked, venting softly over protoform he still hadn’t touched.

Megatron shivered but waved a hand imperiously, again, and said, “If you think you can, Prime.”

With a smile Megatron wouldn’t be able to see, Optimus got comfortable on the berth and refocused his optics on the valve in front of him. It really was lovely. A glowing red nub peeked out between plump swells of black protoform. Optimus moved his hand down to stroke gently along the smooth outer edges of the valve. Using two fingers, he gently spread the soft protoform folds apart, fully exposing the round anterior node and revealing the inner folds around the valve slit. There was a little pool of lubricant that had gathered in the valve and wetted some of the protoform. Not enough yet.

Megatron shifted his hips and complained, “Would you get on with it? At this rate we’ll be here for days!”

Optimus resisted the urge to respond in words and pressed the flat of his tongue in a long, slow, indulgent lick against the little node. Megatron made half a noise before going silent. Optimus continued, looking for the best patterns and touches and motions to get a response out of Megatron. Long slow passes with his tongue were followed by swift flicking licks to the nub, then using his lips to suck on it properly, before releasing it with a pop and beginning again. Megatron stayed scrupulously quiet after that first noise, apart from the gratifying sound of his cooling fans spinning up. His hips kept twitching though, pressing into a desired sensation, or seeking after one when Optimus changed tack. Megatron’s protoform was soft and pliant under his tongue, and he could feel the node starting to throb against his lips when he kissed it.

Lubricant was beginning to spill over the valve rim now, and after a few more kisses and strong sucks to the node Optimus couldn’t resist. He dipped his head lower and licked into the valve opening, tasting the thick, heavy flavor of Megatron’s lubricant, testing the give of the valve walls and seeing how deep he could get with his tongue. When Optimus came back up to pay attention to the node again it was bright and plump, and as he began to lick and suck and slurp at it in earnest, Megatron’s hips bucked up into his mouth.

After Optimus reached an arm from around Megatron’s thigh and began to tease at the valve opening with his fingertips, Megatron shifted again and decided, “Enough!”

Reluctantly, Optimus let his mouth part from the valve with a wet sound.

“Don’t think I don’t know what you’re doing Prime,” Megatron said, sitting all the way up on his elbows. “Like I’m about to let you cheat. If I overload, I’m taking you with me!”

“What do you mean _if?”_ Optimus said, kneeling.

As he looked into Megatron’s optics again, Optimus felt strangely self-conscious about the lubricant decorating his exposed face. This was one of his favorite acts of interfacing, and normally he wasn’t the type to be self-conscious in berth. He was proud of his skills. He was proud of the results he’d earned from Megatron just now—how swollen and wet his valve had become, the tiny little reactions, and the charge Optimus could feel hovering in the air around his opponent, now a match to his own charge.

Still, for all his cooling fans were running high, Megatron looked far from debauched. He was a picture of eroticism… But he seemed in total control of himself.

Optimus’s spike twitched.

“I mean, _if._ You may be able to please your sycophant followers, but I have yet to be convinced.” Megatron spread his thighs just a bit wider and said, “Now, what are you waiting for? Hurry up and let’s see if your spike is worth my time.”

Optimus growled in response and positioned himself on top of Megatron. If Megatron wanted to issue a challenge, Optimus, as always, would meet it.

He took his spike in hand and positioned it at the valve entrance and pushed in. The slick slide of lubricant on the head of his spike immediately sent pleasure throbbing through Optimus’s sensor net. He was far too turned on, it all felt far too good. Then he couldn’t help but look down to where his spike had lewdly parted Megatron’s— _Megatron’s—_ valve lips, seeing and feeling the tight embrace of the channel, and then above that pretty valve was Megatron’s enormous spike, still thick and proud and the stuff of Optimus’s secret fantasies. And Megatron had all the power to go with that incredible spike. He’d be able to really drive into Optimus, really give it to him—

Optimus was thrusting now, without strategy or thought, getting a little deeper each time, and just staring, almost shocked as Megatron’s spike bobbed and swayed with each of his thrusts, and trying desperately to think of some way to make himself last.

He tried looking up, at Megatron’s face, but that was even worse. Megatron was looking down to where they were joined. He was watching as Optimus filled him and pleasured him and there was this incredible look on his face that Optimus had never seen before that jolted with each thrust into his valve. Optimus wanted more. He wanted so much more. More of that look on Megatron’s face, more of the noise of their cooling fans, more of the soft grunts Megatron was making, more of the slick sound of each thrust.  How was he supposed to hold back like this? Able to look down to the largest spike he’d ever seen, the spike he desperately wanted to get to ride? And Megatron was so wet and warm and perfect around his spike.

He would make Megatron overload first, he _would._ He wanted to watch his face.

Optimus moved his weight to one arm without breaking rhythm, and reached his hand between their bodies to rub at Megatron’s sensitive red node. Megatron moaned, then rumbled threateningly, like he was offended that Optimus was successfully pleasuring him. Optimus grinned.

But that look on Megatron’s face never boded well. That calculating frown, that fire in his optics… Then Optimus felt it. Tight, rippling, squeezing, somehow dragging around his spike. Absolutely incredible. The valve had Optimus in such a snug grip it was becoming difficult to thrust.

But two could play at that game. Optimus titled his hips up, changing the angle. There was a set of strong ridges on the top of the Prime’s spike that he knew felt incredible thrusting against the anterior wall of a valve. Optimus pistoned in, hard. Megatron made a sweet sound, startled, before glaring again.

“Well?” Optimus asked. “Is my spike worth your time, Megatron?” He punctuated the question with another thrust.

Megatron growled at him and said, “I haven’t overloaded, or couldn’t you tell?” But there was bravado there, and static in his voice—Megatron was bluffing. He was close. But before he could do anything to hurry him along, Megatron’s hands were on him. He was touching him, grabbing him, along his waist and aft.

They hadn’t, exactly, been touching each other very much before this. All the gentle, tactile play Optimus usually indulged in before interfacing had been skipped, for obvious reasons. Now, Megatron was touching him without reservation, looking for sensitive spots. But even just the search was erotic—Megatron’s hands all over him, groping him, so familiar and yet so sinfully forbidden. Optimus had more than a few easily exploited tender places, and he wasn’t about to give Megatron the time to find one.

Optimus decided to take a gamble. He increased the pressure and sped up the movement of his fingers on Megatron’s node, but he slowed down his thrusts. Not difficult, given how tightly Megatron was squeezing around his spike. Each push in was strong, aggressive, but he kept the stroke out savoring and slow.

Immediately Megatron’s optics widened. Searching hands stopped and grabbed hold. Then Megatron actually _writhed_ underneath him, which was terrible, because Optimus suddenly couldn’t imagine seeing anything more erotic.

Megatron choked out, “Damn you, Prime!” Primus, why did hearing that turn him on. “Don’t you dare—Don’t you dare stop!”

Optimus didn’t stop, though he wasn’t going to be able to withstand the intense pleasure coming from his spike much longer, much less watching Megatron’s reactions. He took his hand from Megatron’s node for just a moment, and touched his own spike with his thumb to gather up excess lubricant. Then he pressed and rubbed the slick digit against the node, hard.

One thrust, two, three, and Megatron actually shouted, “Ah!” and his whole body twisted except for his clenching, fluttering valve as arcs of releasing charge shot white across his plating. Optimus knew he should wait, try to stop and see if he could stave off overload a while longer, but watching that, feeling that, it was too much and he kept thrusting into tight, wet heat. Just as Megatron began to recover enough to glare at him again, Optimus overloaded.

He clutched at Megatron’s hips and held himself deep inside as his spike throbbed in wave after wave of pleasure. In his haze, he felt Megatron’s arms wrap tightly around him...and then they were moving. Optimus reset his optics to find himself flat on his back. Megatron was grinning over him, seated proudly on the Prime’s spike.

“Alright, Prime. I’ll admit you aren’t a complete failure,” Megatron said. Optimus immediately felt nervous. Concessions from Megatron were a dangerous thing. ”But now it’s my turn.”

Trepidation and traitorous excitement warred in the Prime’s spark.  

Megatron spread his hands luxuriously over Optimus’s windshields and he leaned close. “Don’t you dare depressurize,” Megatron purred.

Then Megatron began to do something unspeakable with his valve, that Optimus could only begin to describe as _pulsating,_ all while Optimus looked up at Megatron’s smirking face and his bright, fiery eyes glinting with amusement. The Prime’s spike was instantly stiff and crawling with charge again. Megatron laughed and said, “Very good.” Optimus moaned.

Optimus knew he had to do _something,_ turn the tables somehow, get back control of this encounter, or at least get back control of _himself,_ but then Megatron began to ride him in earnest and he was lost.

His second overload came quick, much to the Prime’s embarrassment. He tried to hold back, but Megatron dragged it out of him, riding him quick and hard and gently stroking along his chest seams like a—like a lover. Megatron’s expression afterwards was infuriatingly smug.

At that point, Optimus still had the presence of mind to give as good as he got, and forced past sensitivity to buck up fiercely into Megatron and offer teasing touches of his own until Megatron was grinding against his abdominal plating, clearly chagrined, and then absolutely stunning to behold, arching in overload on top of him.

After that, the encounter blurred into a series of overloads with barely any space between them. Optimus tried to get up and take back control at least once, but no one was better equipped to hold him down and have his way with him than Megatron, and even that thought was enough to catapult his traitorous frame into overload _again._ Everything was charge and pleasure and Megatron murmuring threats and filthy encouragement and _bouncing_ on top of his spike and trying increasingly creative techniques that convinced Optimus he hadn’t really ever known anything about interfacing at all.

Megatron was confident enough of his mastery that he _denied_ Optimus at one point. Just, stopping what he was doing at just the wrong moment and watching Optimus squirm—not going far enough to make him beg, thank Primus—then starting again and saying the most horrible, wonderful teasing things like, “Oh, did you want me to keep going? Do you need it, Optimus?” until Optimus was sobbing through the most powerful spike overload he’d ever had.

The only comfort for the Prime was that Megatron would occasionally fall into overload with him, or take a break from teasing and torturing to indulge himself with a particular angle or movement—not that watching Megatron drive himself to overload on top of him wasn’t an incredible, beautiful tease in itself.

By the end, Optimus was barely holding onto coherence, nevermind the drive to win. He lost count of the number of overloads he’d endured. Each one seemed like the last his spike could possibly give him.

He’d had multiple overloads in one session of interfacing before. That was even what he was known for among interfacing partners. But never, ever like this. Certainly since he became Prime, his partners had usually been smaller, less powerful. He knew he’d come close—most potential partners he’d had could only handle three or four before edging into sleepy exhaustion. He always stopped when he sensed that sweetly sufficient, satisfied feeling in a partner. He’d never tried to drive someone to their absolute limit before, to the point where automatic system protections engaged to prevent additional overloads. He’d never been driven to his. It was the sort of thing that was difficult to do to yourself, and he’d never even tried.

He hadn’t realized how _intimate_ it would be. It was becoming perilously easy to look into Megatron’s confident face and simply accept what he was given. Inhibitions weren’t even a thought in his processor. Megatron’s perfectly huge spike was still pressurized between them. It had been bouncing and swaying this whole time, and Optimus’s valve ached with want looking at it.

Megatron looked confused, when Optimus reached for it now—he’d tried before, another attempt to bring Megatron over with him, but had had his hand pushed away. But now, as the Prime’s hand trembled, and as he moaned when he discovered how difficult it was to wrap his hand around it, Megatron let him. Optimus loved the sensation of that spike, big and hard and charged in his servo. Like something out of a dream.

“It seems like there's still something you want, Optimus," Megatron said. He put his hand over the Prime’s on his spike. Optimus could only keen. “It may take us a little longer to manage. Are you quite sure?”

Optimus nodded.

Megatron leaned close now and rested his hand on the Prime’s face, one thumb pressing softly over his lips. “We hardly need to. I’ve proved I can take you all the way to the edge just like this.”

It was a struggle, getting his vocalizer to form real words. But Optimus had never wanted anything quite like this before. “Please.”

Then again, “Please, Megatron.”

Optimus could feel the shuddering of Megatron’s vents and the flutter of Megatron’s valve around him in response. Then his lover was lifting off of his spike and reclining down beside him. Megatron tapped the sensitive spike and said, “Go ahead and let this depressurize for me.”

Without waiting for him to obey, Megatron lifted one of Optimus’s thighs and arranged him so he was spread wide. Optimus revealed his valve to Megatron’s expectant gaze without being asked.

He felt exquisitely vulnerable. He had to resist the urge to beg.

Though that resistance didn’t last long. Megatron was smiling at him and working him open with his fingers. Optimus hardly felt the first one enter him until it was stroking his walls inside, he was so incredibly well-lubricated already. It was just how he’d imagined it when he’d first seen that spike, except Megatron’s expression wasn’t actually smirking. Optimus didn’t know what that expression was. Optimus was writhing by the time the second finger was in his valve, spreading him. Partway through three fingers he started to beg. At four, he went silent and could only pant and shiver.

“I think you might be able to accommodate me after all,” Megatron said, looking on as his fingers spread open the dripping valve walls. Megatron actually revved his engine at the sight, growling down at him. “I’m sorely tempted to explore your lovely little node, but I’m not sure how many overloads you have left to give me, and I confess, I want to see you overload around my spike.”

Optimus had no idea how much longer Megatron spent preparing his valve, but by the end he was ready to swear that the warlord’s incredible reserves of patience ought to be considered criminal. Finally, Megatron removed his fingers and settled on top of him. Optimus spread his legs just a bit wider. He was half convinced now that this was a particularly vivid dream. Reality couldn’t possibly be so good.

Lubricant-wet fingers brushed against his face and Megatron ordered, “You will tell me if there is any pain or if you see any errors.” Optimus nodded. But that wasn’t good enough. “No, Prime. I want your word. I know how your honor works.”

Shaking with anticipation, Optimus said, “I promise.”

Optimus felt something huge brush against his valve and a tingling snap of charge grounded itself against his anterior node. Megatron murmured, “Perfect.”

For all he was expecting it, the pressure was shocking. There was a terrifying moment when Optimus thought _it wouldn’t fit,_ and most horribly, _he might not get to have this,_ but then Optimus felt his whole valve cycle open wide around the intrusion. He could feel a delicious tugging on his anterior node as the soft protoform of his valve was stretched to accommodate Megatron’s spike.

Megatron was looking down at Optimus’s face as the spike entered him, steady and slow. Optimus, already out of practice controlling his expressions, didn’t have the spare processor space even to try looking less devastated by the sensations. He was sure he looked debauched. Megatron only smiled at him softly, lips parted. Then he shifted his gaze to the Prime’s straining valve, expression unchanging.

Megatron moved a hand off the Prime’s hips and traced a slow, horribly gentle path with one finger around the ever-so-stretched rim of his valve. Optimus shivered, and his valve tried to tighten and found it couldn’t. Megatron massaged the strained protoform where his spike was opening Optimus up and the sensation—Optimus warbled a needy, gasping sound.

Megatron pushed further in, inexorably, fully, what a gorgeous, open feeling, and Optimus couldn’t help crying out with each little push forward, “Ah! Ah! Ah!” and “Megatron!” But his vocalizer kept shorting out after the first two syllables of Megatron’s name, and Optimus found himself chanting it, trying to get it right.

There was a hand on his helm, soothing, and Megatron’s voice close to his audial, saying “How marvelous you are.” Optimus could barely see for all he was feeling, but when he tried Megatron’s face was right there before him, looking, looking intent—intent on him, focused completely on his reactions and Optimus tried to twist his helm, feeling exposed, but Megatron was holding him gently. When he looked again there was an openness to Megatron’s expression that he’d never seen before. He stared up helplessly at Megatron’s face as the rest of the spike was pressed into him. He had never felt like this, never. There was a ridge, or perhaps a set of ridges toward the base, though they were much less pronounced than the ones on Optimus’s own spike. Optimus had barely noticed them when he was looking, but _now,_ stretching him just that barest bit more—Megatron frowned in concentration as he began to push past the first ridge—

And just like that, Optimus overloaded.

Distantly, he could hear himself shout Megatron’s name, but all his senses were focused on his valve. So impossibly tight, so impossibly wet, and aching so deeply, so perfectly, the throb and the charge of Megatron’s spike still pushing him higher.

When he could see and hear and feel properly again, Megatron’s hands were trembling on his hips, holding on, and Megatron had curved his whole body over Optimus to rest his helm against the Prime’s chest. Optimus felt his valve flutter and relax, just enough. Megatron’s spike suddenly slid the rest of the way inside. Megatron moaned low.

His lover looked up at him and all at once Optimus ached to touch him. Optimus reached out for the powerful arms and chest, just stroking over Megatron’s plating, still enjoying the unending stretch. He wrapped his arms around Megatron’s neck and held on.

“Would you like more?”

Once more, softly, Optimus said, “Please.”

Megatron groaned and nuzzled his face into Optimus’s neck. They were cheek to cheek, and Optimus pressed into the touch. Enormous hands stroked his hips, and then Megatron was rocking forward, and Optimus’s world began to fly apart again.

Every moment of this became vividly inscribed in his mind, but without order. An endless march of overwhelming pleasure. Megatron kept up that shallow, rocking pace for an age, no matter how Optimus pleaded, and then he went light and quick, a gentle and unbearable agony that left Optimus losing count of his overloads again. Once, Megatron stopped moving altogether and just stroked at his nub as Optimus tried and tried to squeeze around the deliciously charged spike inside him. Megatron spilled in him at least twice, and each time the look on his face made Optimus’s spark throb.

Optimus lost all control over the volume of the sounds he was making, the things he was saying—shouting, and he didn’t care because every new plea, every new cry, made Megatron moan and growl and hold him close. Megatron asked him if he could stand to keep going, and all Optimus could do was cry out, “Yes! Forever! Please, perfect, perfect, _you,_ forever—”

They never did make it to the powerful, unrelenting pounding that Optimus had imagined Megatron would give him. But, at last, Optimus’s begging earned him a response, roughly spoken among Megatron’s own gasps, “Do you want me to take you properly? Do you want me to take you hard, Optimus?”

Of course he said yes. And Megatron stilled, looking down at him, adjusting. Both of them tense, waiting, and Optimus could hardly stand it. Then Megatron thrust in, hard and strong and controlled and Optimus heard himself scream in pleasure. Two hard thrusts and Optimus was shaking and falling over the edge for the last time. It was at most six thrusts, each one driving Optimus impossibly higher, before he saw the first look of overload on Megatron’s face—he knew that expression now—but by then his own overloading frame had dragged him blissfully into stasis.

 

* * *

 

“Can you not move, Prime?”

Optimus shifted a bit, and moaned. Getting up...would be difficult. He was lying half on top of Megatron. Several parts of him ached deliciously. His short term memory was rebooting, and flashes of extraordinary pleasure were echoing across his sensor net. In the present, he felt incredibly warm—Megatron must have pulled a blanket over them—and each of his limbs and joints was experiencing a delightfully loose sensation. Everything felt surprisingly clean, and he found his panels had been closed.

As he came back to himself, he realized, or remembered, that Megatron had very clearly _won,_ and that their arrangement was _over,_ and something in his emotional subsystem was rioting at both of those things, so he tried to move again, but he couldn’t, actually, at all, and he was completely at Megatron’s mercy—

Megatron tightened his grip on the Prime’s waist in response to the rising tension. Then he resumed stroking a long blue finial in slow, soft pulls. A shivering relaxation spread throughout Optimus’s body from his helm to his pedes. When had Megatron discovered that trick?

“Worry not. I only violently eject berth partners when they fail to satisfy me.” Megatron hummed a bit, thoughtfully. “And you were adequate, I suppose.”

Optimus didn’t have to look to know he was smiling, the slagger. Optimus managed to get one sardonic word out of his vocalizer, “Adequate?”

“Oh yes. Very adequate.”

Optimus started grumbling, loudly, but Megatron tugged on the finial in his hand, gently, and a wave of sleepy pleasure rocked through Optimus and he sighed quietly instead. He snuggled closer. Megatron was big and warm.

“Actually, I should give you credit. There aren’t many who can take my spike at its largest size. Quite impressive.”

It took a moment for Optimus to process that.

“Its what?” he managed.

“Mm. Did I forget to mention?”

Optimus tried to wriggle around so he could glare properly, but Megatron was inexorably insisting on cuddling and wouldn’t release him. None of the Prime’s motor functions were responding well at the moment, which didn’t help. Wordless, he made a questioning, complaining noise.

“Settle down. I must have forgotten to tell you. My spike has a mass-shifting mod, of course.”

Optimus spluttered, voice still full of static, “Forgotten to tell me!”

Megatron chuckled, and the vibration against his chassis was annoyingly soothing.

“Alright, I’ll confess. It seemed expedient to start our encounter using my valve, so I omitted that detail. Little did I suspect you would like my spike so much at its largest size, in the end.”

Wordless, Optimus could only growl accusingly. Megatron responded, “Yes, rather an underhanded strategy, but I can’t say I’m sorry for it. Things took longer this way, which is for the best as well.”

Optimus revved his engine, but, beginning to feel a sinking sensation in his spark, said, “I can’t claim that breaks our agreement...”

Megatron petted him again and actually _laughed,_ like this was _funny,_ the future of this planet, how could Optimus have been so _reckless—_

“Oh, the agreement doesn’t matter. If you’ll remember, one of the stipulations was a ceasefire for the duration, and I’ve already broken that rule. Starscream led a raid for me while we were otherwise occupied.”

Optimus could only stare at the swathe of Megatron’s chest plating that was he could see from this angle.

“I haven’t checked in with them yet, but unless Prowl suspected the plan, it ought to have gone quite simply.”

Optimus tried to push away again, but Megatron held him fast. And he still had almost no strength in his limbs. “Don’t be upset. It was only a small weapon, and, hopefully, quite a large amount of the humans' fuel. So relax, Prime. I’m certainly not going to hold you to your end of the bargain.”

His spark spun wildly in his chest as he cycled through a series of emotions: doubt, confusion, anger, extreme relief, and back to anger again. Optimus tried getting up again, and when Megatron still wouldn’t let him, he honked, very rudely, at him.

Megatron loosened his grip. It took some doing, but Optimus managed to prop himself up on his arms slightly. Megatron had a wary look on his face. Optimus let his engine rev, and then, voice insistent, said, “I don’t _believe you!_ Adequate?!”

Megatron’s expression cracked into something that might have been amusement.

“Adequate! Like you aren’t going to be self-servicing over this for the next millennium! I saw your face!” Optimus accused.

“I think not, Prime.” Megatron let a smug smile spread across his mouth. “After all, why bother with self-service when you can have more of the real thing?”

Optimus actually managed to sit part way up this time, so he could look directly into Megatron’s face, and stared, frowning. “What?”

It was strange, it looked like Megatron’s expression softened just then. Must have been a trick of the light.

“I haven’t forgotten all those charming things you shouted when you were squirming on my spike,” Megatron said. Optimus’s valve throbbed, trying and failing to become aroused again, as the memory flashed through his processor. The memory of all the very many things he had said. Megatron continued, grinning now, “You’re hardly about to give this up.”

Optimus tried to glare at him, and then he tried to remember the reasons why a repeat performance of the best pleasure he’d ever experienced would be a _bad_ idea.

His lover smiled again and pulled him back down to lay on his chest. Optimus grumbled, but went. Then he felt something warm and soft on his helm finial. Megatron was...kissing him there? Gently. Sweetly. A delightful tingling sensation swept through his sensor net. But Optimus was still slightly annoyed, and he flicked the finial into Megatron’s face.

Megatron only laughed, and pulled him in close.

**Author's Note:**

> Meanwhile, Jazz and Soundwave are awkwardly standing guard outside and avoiding eye contact when they overhear Optimus screaming things like 'please harder Megatron' and 'Primus you feel so good.'
> 
> Thank you to [RHplus](https://archiveofourown.org/users/RHplus/works) for checking for errors in her own gift ;)
> 
> All feedback cherished. [Find me on twitter](http://www.twitter.com/perictione1)!


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